The increase in the prevalence of enamel fluorosis in the US, Norway, and elsewhere in the Western world has been a cause of concern within the dental research and public health community. Enamel fluorosis has important public health importance since fluoride is an important caries preventive agent. Thus there is need to very specifically identify early fluoride exposures responsible for this increase in enamel fluorosis prevalence. Findings in Norway have important relevancy to the US. Evidence suggests fluoride supplement use under pre-1994 US protocols was an important risk factor for enamel fluorosis. In 1994, a lower dosage protocol was accepted in the US, which is remarkably similar to a protocol under which current middle school age children in Norway were supplemented from infancy. This creates an opportunity to investigate whether there is continued fluorosis risk associated with this protocol, years in advance of our ability to conduct such an investigation in the US. In contrast to the US, Norway has never artificially fluoridated any of its drinking water supplies, and the presence of naturally occurring fluoride is relatively rare, so there is no fluoride "halo effect." Thus estimates of fluorosis risk associated with fluoride supplement and early fluoride dentifrice use derived from an investigation of a Norwegian population will represent conservative minimum estimates of the fluorosis risk potential of these fluoride sources in the US. This case-control study will investigate fluorosis risk factors among Norwegian children, age 11-13 years, living in Bergen, Norway. The methodology, including use of the Fluorosis Risk Index (FRI) and a mailed questionnaire, has been consistently used successfully in 5 previous risk factor studies. The FRI has consistently demonstrated good reliability. The questionnaire has consistently demonstrated a high response rate, high test/re-test reliability, and the ability in conjunction with FRI subject fluorosis categorization to identify strong associations between age-specific exposures and surface area-specific enamel fluorosis. Logistic regression analyses will be used to derive adjusted odds ratio estimates of the relative risk of enamel fluorosis associated with early fluoride exposures as well as adjusted estimates of attributable risk. Caries examination will allow comparison with fluorosis and early fluoride exposures.